The sixth Fairford suspect, a UK-Iranian dual national aged 25, is released on bail

British counter-terrorism police have released on bail a 25-year-old UK-Iranian dual national arrested on Thursday in the London borough of Westminster in the RAF Fairford investigation. He had been held on suspicion of preparation of terrorist acts. Searches of two properties in the same borough are finished. The investigation continues.

He is the sixth man bailed in the file. Five others, UK nationals from London aged between 23 and 25, were arrested in the early hours last weekend on suspicion of explosives offences and later on suspicion of preparing a terrorist act. Police released them on bail on Monday and called the decision an investigative one, grounded in experience and strategy. All six are now on bail. None has been charged in the public account.

The incident that opened the file was a report of three suspicious vehicles near RAF Fairford in Gloucestershire, a base used by the US Air Force. A major incident was declared. Dozens of homes were evacuated. The BBC reported that one of the five men dialled 999 himself, about an hour before a local farmer alerted police to a large group of masked men near the vehicles. That call is the awkward fact in the explosives theory. A suspect who phones the police before a farmer does is either raising the alarm or creating a record. The investigation has not said which.

Fairford is the Gloucestershire field the United States uses for bomber deployments. A report of vehicles and masked men near it, days after other Iran-linked cases in Britain, produced a large police response and a weekend of evacuated houses. Bail for all six, with searches in Westminster completed, means the public evidence has not yet supported a charge the police are ready to lay. Bail is not a finding of no case. It is a decision that the arrest power has done its immediate job and the file is not ready for a courtroom.

The sixth arrest, on Thursday, widened the file from the five men held at the weekend to a dual national picked up in Westminster. Releasing him on Saturday, after the two property searches ended, puts him on the same legal footing as the others. Police did not name him. They did not describe what the searches found. They said the inquiry into the circumstances is continuing.

What a reader can check is the sequence. Vehicles reported near Fairford. A 999 call from one of the men, about an hour before the farmer's call. Five arrests, ages 23 to 25, London, explosives suspicion upgraded to preparation of terrorist acts, bail on Monday. A sixth arrest on Thursday, UK-Iranian, 25, Westminster, same suspicion, two properties searched, bail on Saturday. No charge sheet has been published.

The open question is whether the 999 call becomes the centre of the file or a footnote. If the caller was warning of the other men, the masked-group account and the suspect list may not be the same set of facts. If the call was part of the approach to the base, it is evidence of a different kind. Police have not said. Until they do, the verified update is the sixth bail, the completed Westminster searches, and a base investigation that has not yet produced a charge.